NASA revealed on Dec. 30 that the NEOWISE mission has found two new near-Earth objects. One is not distinctly an asteroid or comet, and the other is a comet.
Comet-Asteroid Object 2016 WF9
The NEOWISE project, the asteroid-hunting portion of the Wide-field Infrared Survey Explorer mission, detected the comet-asteroid object known as 2016 WF9 on Nov. 27. The object tours the solar system over the course of 4.9 Earth-years, following the orbital path of Jupiter as it approaches the sun and swinging inside the orbits of Mars and Earth before it heads back to the outer solar system.
Scientists estimate that the object is relatively large, spanning about 0.3 to 0.6 miles across. It is also dark, reflecting only a few percentage of the lights that strikes its surface. Astronomers said that these objects look like charcoal and sometimes even darker than that.
Not Distinctly A Comet
Although the body looks like a comet based on its reflectivity and orbit, it does not have the dust and gas clouds that characterize comets.
"This object illustrates that the boundary between asteroids and comets is a blurry one; perhaps over time this object has lost the majority of the volatiles that linger on or just under its surface," said James Bauer from the Jet Propulsion Laboratory.
2016 WF9 is predicted to approach Earth's orbit on Feb. 25 at a proximity of nearly 32 million miles. Scientists understand the trajectory of the object well and 2016 WF9 does not appear to pose any threat to Earth in the foreseeable future.
Comet C/2016 U1 NEOWISE
The other celestial body detected by NEOWISE is called C/2016 U1 NEOWISE. Unlike 2016 WF9, it releases dust as it approaches the sun and is distinctly a comet.
The comet can be seen from the northern hemisphere on the first week of 2017. Astronomers said that there is a good chance the object can be seen using a good pair of binoculars. There are uncertainties though due to the unpredictable nature of the comet's brightness.
The object will reach its closest point to the sun inside Mercury's orbit on Jan. 14 before it heads back toward the outer solar system for an orbit that lasts thousands of years. The comet does not pose any threat to our planet.